The photon torpedo was developed as a tactical weapon that could be used while a starship is
traveling at warp - a situation in which phasers are useless.

First developed in 2215, photon torpedoes are explosive weapons which, unlike phasers, can be fired at
warp speed. They are carried as standard on most Federation starships, and are often fitted to space
stations such as Deep Space 9.

The photon torpedo took some time to fully develop. Casing and delivery systems were in place early in
the 23rd century, but the first models had a range of just 750,000 kilometers and produced a relatively
low explosive yield. A much more advanced photon torpedo now exists; this latest model has an upper
range limit of 4,050,000 kilometers, as fire from a starship at warp. If launched from a stationary
platform, the torpedo will never reach warp 1, and therefore cannot travel nearly as far. This range
can be extended, but because the engine draws fuel from the matter-antimatter tanks, this can be done
only at the expense of the torpedo's destructive power. The photon torpedo's explosive power comes from
the matter and antimatter packets, which are usually delivered at warp speed by a small matter-antimatter
fuel cell, then thrust together to cause an explosion. The torpedo has a lozenge-shaped casing made of
molded gamma-expanded duranium and a plasma-bonded terminium outer skin. The latest casing measures 2.1
by 0.76 by 0.45 meters, an weighs 186.7 kilograms.

When used as a weapon, the torpedo contains explosive material, target acquisition, guidance, detonation
assemblies, and a warp sustainer engine. Due to its small size, the warp sustainer engine is not a true
warp engine, and is more accurately described as a matter-antimatter fuel cell. If the torpedo is
launched at warp speed, the sustainer coils in the fuel cell acquire warp velocity from the torpedo
launcher tube. The matter and antimatter are carried aboard the torpedo in tiny packets; this method
increases the effective contact area by three orders of magnitude over the same amount of matter and
antimatter safety measure, the packets are kept far apart within the torpedo until just after launch.
The photon torpedo carries a maximum of only 1.5 kilograms of antimatter, but the use of packets yields
destructive power greater than that caused by a
Galaxy-class antimatter pod rupture. It is an impressive
weapon in the Starfleet arsenal.